The present invention is related to cardiac pacemakers and stimulation circuits of a defibrillator or cardiovertor, and more particularly to their utilization for the treatment of cardiac insufficiency by stimulation.
In addition to treating irregularities of the cardiac rhythm by stimulation, it is also known to so treat irregularities of myocardial contraction observed in patients with cardiac insufficiency, whether spontaneous or induced by a traditional stimulation. A study by J. C. Daubert et al., Stimucaur, Volume 25, no 3, pp. 170-176 surveys works on this subject.
xe2x80x9cMultisitexe2x80x9d pacemakers are known for stimulating the right and left cavities of the heart. In these multisite pacemakers, electrodes are placed in a plurality of respective distinct sites of the heart, including at least one ventricular site. These devices can provide double ventricular stimulation, double ventricular stimulation with right atrial stimulation (so called xe2x80x9ctriple chamberxe2x80x9d models) or double ventricular stimulation with double atrial stimulation (so called xe2x80x9cquadruple chamberxe2x80x9d models).
In double ventricular treatments, the stimulation of the two ventricular sites must be simultaneous. This is typically accomplished by use of a classic pacemaker comprising a bipolar connector for ventricular stimulation, to which a particular probe comprising a  less than  less than Y greater than  greater than  adapter is connected where one end of the adapter (i.e., the bottom of the  less than  less than Y greater than  greater than ) allows a bipolar (i.e., two conductor) connection to the connector of the pacemaker, and the other end (i.e., each of branches of the  less than  less than Y greater than  greater than ) allows a connection of two unipolar probes, each corresponding to one of the two respective conductors of the bipolar part and ending at the two ventricular sites, right and left. Such a configuration allows transformation of the bipolar output of a classic pacemaker into two simultaneous unipolar outputs.
Nevertheless, the utilization of such a  less than  less than Y greater than  greater than  connector is not without its disadvantagesxe2x80x94both at the moment of implantation, since it is necessary to put in place and to safely lodge the connector, and later (in terms of reliability), particularly due to the difficulty of maintaining a perfect seal against organic fluids surrounding the connector.
Furthermore this assembly, once put in place, systematically produces double stimulation (of the two ventricular sites), without it being possible later (after implantation) to suppress one stimulation, for example, following the elevation of threshold on one of the probes, except of course by a new intervention.
One of the objects of the present invention is to overcome these various disadvantages by allowing double simultaneous stimulation of two ventricular sites (and/or two atrial sites) with no intermediate  less than  less than Y greater than  greater than  connector, thereby avoiding all the attendant difficulties of this particular adapter.
Another object of the present invention is to provide a device that can individually command either one or the other, or both, stimulations, for example, by selectively programming either double ventricular stimulation, stimulation of the right ventricle alone or stimulation of the left ventricle alone, the selection being implementable and operable in a non-invasive manner and by means of a known device such as a programmer associated with the pacemaker, for example, via telemetry.
A further object is implementation of the present invention in preexisting models of classic pacemakers, for example, the Chorum(trademark) series of products available from the assignee hereof, Ela Medical, with modification necessary only to the output stage by incorporation of an additional circuit, avoiding redesign of the main circuit of the pacemaker or the control software thereof.
More preferably, the pacing device of the present invention is a pacemaker of the aforementioned xe2x80x9cmultisitexe2x80x9d type where electrodes are placed in a plurality of respective distinct sites including at least one ventricular site and are connected to a cardiac signal collection circuit for detecting a depolarization potential at the corresponding site, and to a stimulation circuit for applying, when necessary, a stimulation impulse to the same site, characterized in that the pacemaker comprises programmable selection means to selectively connect the stimulation circuit that is common to them, and either one and/or the other of the right and/or left electrodes of the particular cavity.
In an alternative embodiment of the present invention, each of the electrodes possesses a connector with the selection means disposed between the stimulation circuit and the respective connectors of the electrodes.
In a further alternative embodiment, a stimulation impulse can be simultaneously applied on these two electrodes when the selection means select and consequently connect the two electrodes, right and left, to the stimulation circuit.
In another embodiment, the configuration of the selection means can be defined by a programmer temporarily coupled to the pacemaker, for example, by telemetry.
In yet another embodiment, the plurality of respective distinct sites includes at least one ventricular site and two atrial sites, distinct ventricular stimulation means and atrial stimulation means are provided, and the selection means is programmable to selectively connect one and/or the other of the right, and/or the left, ventricular electrodes to the ventricular stimulation circuit, and to selectively connect one and/or the other of the right and/or left atrial electrodes to the atrial stimulation circuit.
In another alternative embodiment, the additional components of the selection means are mounted on a flexible circuit connected to the main circuit of the pacemaker which also supports the components of the stimulation circuit.
Preferably, the stimulation circuit is a programmable circuit, which is programmable in either a monopolar or bipolar stimulation mode, where the selection means causes application of the stimulation impulse to one of the electrodes when the circuit is programmed in monopolar mode, and to two electrodes when the circuit is programmed in bipolar mode.